Filament spool



FIG. 1 is a top perspective view of a filament spool;

FIG. 2 is a top view thereof, where a bottom view is identical to the top view;

FIG. 3 is a front view thereof, where a rear view is identical to the front view; and,

FIG. 4 is a right side view thereof, where a left side view is identical to the right side view.

The features shown in broken lines illustrate environmental subject matter only, and form no part of the claimed design. 

CLAIM The ornamental design for a filament spool, as shown and described. 